It all started when Rikka, a student he had a crush on, approached him and gave him a spare key. For a month during summer vacation, Rikka frequented his teacher's house, and they practically lived together. They made hamburgers together, squeezed into the small bathtub, and had sex every single day. A fleeting and heartbreaking story of a relationship they couldn't tell anyone about, which might one day come to an end...